Light receiving/emitting device with both a light receiving function and a light emitting function has been used in electronic information equipment such as photocopiers, facsimiles, and scanners (for example, refer to Patent Literature 1). There has been also conventionally suggested an image display device in which light emitting cells and light receiving cells are provided in pixels to detect the position of an object contacting or approaching a display screen (refer to Patent Literature 2). In the device described in Patent Literature 2, a light emitting unit is formed by an organic light emitting element and a light receiving unit is formed by a photodiode, for example.
In each of the devices described in Patent Literatures 1 and 2, the light receiving elements and the light emitting elements are arranged on one and the same plane. There is also a light receiving/emitting element in which the light receiving unit and the light emitting unit are laminated (refer to Patent Literature 3). In the information reading element described in Patent Literature 3, the light receiving unit is formed by an organic photoelectric conversion element with light permeability, and the light emitting unit is formed by an organic electroluminescence element.
There has also been suggested a light receiving/emitting element in which an organic layer is formed from an organic material having the light emitting function at the time of application of a forward bias and having the photoelectric conversion function at the time of application of a reverse bias, and which can switch between light emission and light reception by changing a bias voltage to be applied to the organic layer (refer to Patent Literature 4). The light receiving/emitting element described in Patent Literature 4 acts as a light emitting element when a forward bias is applied to the organic layer, and acts as a light receiving (imaging) element when a reverse bias is applied to the organic layer.